Final answer:
The phrase 'nomini Romano' suggests a Latin grammatical case, likely the dative, indicating 'to the Roman name' or 'for the Roman name.' The specific case usage depends on the phrase's syntactical role in the sentence.
Step-by-step explanation:
The question 'What case is nomini Romano and why?' is asking about a grammatical case in Latin. Latin is an inflected language where the endings of nouns change to express their role in a sentence, and 'nomini Romano' appears to refer to a form in a particular case. Unfortunately, without further context, it's challenging to provide a definitive answer to the 'why' part, as it would depend on its function in a sentence. However, if 'nomini' is taken to be in the dative case, which is typically used to indicate the indirect object, it could be translated as 'to the Roman name' or 'for the Roman name.' The reason for it being in the dative case would be governed by its syntactical relationship to other elements within the sentence in which it is found.